Flu vaccine may slash Alzheimer's risk: Here's what dose to get

A higher dose of the flu vaccine may cut Alzheimer’s risk by more than half, research suggests. Image credit: alvarez/Getty Images This article originally appeared on Medical News Today Researchers have been looking at already-used vaccines to potentially help lower risk for Alzheimer’s disease and other types of dementia.

One such vaccine is the influenza vaccine, which previous studies show may help lower a person’s dementia risk. A new study found that older adults who receive a high-dose influenza vaccine may lower their Alzheimer’s disease risk more than those receiving a standard vaccine dose.

As researchers continue to find new ways of helping to reduce a person’s risk for Alzheimer’s disease and other types of dementia , some are examining vaccines that are already being used to lower risk for other diseases. For example, a study published in December 2025 found that the shingles vaccine might help lower a person’s risk for dementia, as well as slow disease progression.

Other published research shows that vaccines like the tetanus and diphtheria (Tdap/Td) vaccine , pneumococcal vaccine for pneumonia , and influenza vaccine for the flu might also help reduce a person’s Alzheimer’s disease and dementia risk. Now a new study published in the journal Neurology reports that older adults who receive a high-dose influenza vaccine may lower their Alzheimer’s disease risk more than those receiving a standard vaccine dose.

Low-dose vs high-dose flu vaccine: How does it affect Alzheimer’s risk? Paul Schulz , MD, professor and neurologist at UTHealth Houston, and lead author of this study, explained to Medical News Today that this new study continues previous research, including a study he and his colleagues published in 2022 .

The 2022 study found that the influenza vaccination may help reduce the risk of Alzheimer’s disease by up to 40%, with six annual vaccinations. “The nagging question after these studies was whether we had a true finding versus a spurious one due to ‘the healthy survivor effect,’ also called ‘the healthy vaccinee effect’,” Schulz told MNT.

“That means that folks who get vaccinated may generally have a healthier lifestyle: Just like they get vaccinated, they also exercise, take their blood pressure and cholesterol medications , see their doctors regularly, eat healthier, etc.” – Paul Schulz, MD “Serendipitously, I gave a talk at the Houston Public Health Department, and they asked whether there was a dose-dependent effect,” he continued. “I wasn’t aware that folks over age 65 get a vaccine that is four times the strength of the standard vaccine due to our immune systems being less responsive as we get older.“ “But, it turns out that not everyone over age 65 gets the high dose influenza vaccine.

The health department and pharmacies can run out of the high dose, etc,” said Schulz. “That led to the paper [where] the goal was to test whether, when we enrolled only people who were vaccinated [whether with a high or low dose], there was still a protective effect of vaccination on reducing Alzheimer’s disease risk,” he added.

High-dose protective effect stronger in women After analyzing health data from about 200,000 participants ages 65 and older, researchers found that those who received the high-dose influenza vaccine lowered their Alzheimer’s disease risk by about 55%, compared to 40% with those who received the standard vaccine dose. Additionally, scientists reported finding the protective effect of the high-dose flu vaccine was stronger in women than men.

“We don’t know why that is, but we do know that women and men’s immune systems are very different,” Schulz said. “Men tend to have a stronger innate immune response (recognizing pathogens as foreign the first time we see them) and women tend to have a stronger antibody-mediated response.

The antibody response is how vaccines work, of course, by having us make antibodies that are ready to attach to pathogens to which we are exposed,” he continued. “So, our hypothesis is that women may have a more vigorous immune response.

And, immune activity is involved in how brain cells are lost in Alzheimer’s disease. So, a more vigorous immune response to vaccines could translate into a greater effect of vaccines in women.” – Paul Schulz, MD How might the flu vaccine help lower Alzheimer’s risk?

Questions remain as to how a vaccine for the flu might help lower a person’s risk for Alzheimer’s disease. Dung Trinh , MD, an internist for MemorialCare Medical Group and chief medical officer of the Healthy Brain Clinic in Irvine, CA, told MNT there are a few biologically plausible possibilities.

“First, high-dose influenza vaccines generate a stronger immune response than standard-dose vaccines in older adults, and that may reduce the likelihood or severity of influenza infection and the systemic inflammation that comes with it,” Trinh, who was not involved in the recent study, explained. “Since chronic inflammation and neuroinflammation are thought to play a role in Alzheimer’s disease, reducing inflammatory stress over time could be one pathway,” he hypothesized.

“Second, there is growing interest in the idea that some vaccines may ‘train’ or modulate the immune system in ways that influence brain health more broadly, although that remains theoretical,” he continued. “The important point is that this study does not prove the mechanism; it raises a credible hypothesis that stronger protection against infection, stronger immune stimulation, or both could contribute to lower risk of Alzheimer’s.” Trinh said.

Promising findings with more research needed MNT had the opportunity to speak with Rehan Aziz , MD, DFAPA, vice chair of education, psychiatry at Hackensack Meridian Jersey Shore University Medical Center, and associate professor of psychiatry and neurology at Hackensack Meridian School of Medicine in New Jersey, who commented he was excited about the study’s findings. “We already have compelling data suggesting that the shingles vaccine may reduce the risk of Alzheimer’s dementia, and this new study indicates that the flu vaccine could offer a similar protective benefit,” Aziz, who was likewise not involved in this study, explained.

“In my practice, I already recommend the shingles vaccine to older adults not only for its primary purpose but also for this potential cognitive benefit. Now, we can extend that same reasoning to the annual flu shot,” he told us.

“Furthermore, this study provides a strong clinical rationale for recommending the high-dose flu vaccine specifically, as it demonstrated a greater reduction in Alzheimer’s risk compared to the standard-dose version,” he added. MNT also spoke with Peter Gliebus , MD, chief of neurology and director of cognitive and behavioral neurology at Marcus Neuroscience Institute, a part of Baptist Health South Florida, who said he found this research promising.

“However, the study’s limitations, such as a short follow-up period and reliance on claims data, mean the findings should be interpreted with caution,” Gliebus, who was also not involved in the study, said. “More research is needed to confirm these results and understand the mechanisms involved.” “Future research should include longer follow-up studies, randomized controlled trials, and investigations into the biological mechanisms behind the protective effects of high-dose influenza vaccines,” he detailed.

“Studies should also focus on diverse populations, incorporate biomarker data, and explore the vaccine’s impact on cognitive decline progression.”